CF33-hNIS-antiPDL1 enhances immunogenicity and anti-tumor efficacy in an orthotopic syngeneic pancreatic cancer mouse model

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a tumor-protective immune microenvironment that limits the efficacy of current immunotherapeutic agents, underscoring the need for novel strategies. We previously demonstrated that CF33-hNIS-antiPDL1 possesses potent oncolytic properties against human PDAC in vitro and in immunocompromised mouse models. In this study, we investigated the immunogenic properties and therapeutic efficacy of CF33 derivatives in murine pancreatic cancer KPC cells in vitro and in an orthotopic syngeneic mouse model. CF33 derivatives replicated in and killed KPC cells in a dose- and time-dependent manner. KPC cells stained negative for surface PD-L1 but positive for intracellular PD-L1. Treatment with IFNγ and IFNβ1, cytokines involved in viral response and immune regulation, significantly upregulated cell surface PD-L1 expression on KPC cells. Notably, infected KPC cells produced virus-encoded anti-PD-L1 single-chain variable fragment (scFv) that blocked IFNγ/β1-induced surface PD-L1 binding. In vivo, intraperitoneal administration of CF33-hNIS-antiPDL1 significantly prolonged survival in mice bearing orthotopic KPC tumors. This benefit was associated with a notable increase in CD45⁺ leukocytes and CD8⁺ T cells. In conclusion, CF33-hNIS-antiPDL1 showed both immunogenic and anti-tumor activity against mouse KPC cells in vitro and in vivo, with functional expression of active anti-PD-L1 scFv. These findings support the clinical translation of CF33-hNIS-antiPDL1 as an intraperitoneal therapy in PDAC patients.